This invention relates to the production of magnetic recording disks and more particularly to a method of smoothing the media to increase the recording capacity of the flexible disk.
U.S. Pat. Nos. 4,874,633 Kasaga et al., 5,804,283 Inaba et al., and 5,851,622 Ejiri et al. relate to a method of producing magnetic recording media used by Fuji Photo Film Co. This process is often referred to as a xe2x80x9cwet on wetxe2x80x9d process. For the typically flexible high density media, the substrate is between 30 and 60 microns thick and has bumps which facilitate the unrolling of the film. The bumps may be one or two microns tall. A planarizing layer is applied to the substrate to cover most of these rough spots. Then the magnetic layer is applied which has particles and binders. One of the last steps in the process is to pass the web of media through rolls in a calendaring process which flattens the web of media. In some instances an attempt is made to burnish the media. However, it is well known that even with calendaring and burnishing the media still has bumps which are quite large in the scale of magnetic recording wherein disparities in the range of 30 nanometers or larger present a problem. If a magnetic recording head hits the disparity this causes the head to ride over the disparity and causes spacing loss preventing effective recording on some areas oft he material.
A continuously running web of media is cut into disks which are referred to as xe2x80x9ccookies.xe2x80x9d The xe2x80x9ccookiesxe2x80x9d cut from the web material are made into flexible magnetic recording disks used in cartridges for flexible media magnetic recording systems such as the ZIP and Clik! storage systems made by Iomega corporation. These recording systems have increasingly higher data capacities. The higher density recording requires an exceptionally smooth recording system.
One of the critical processes in making the cookies into disks for high capacity recording cartridges is laying down servo tracks on the media. This is typically performed by a very expensive machine that has exceptionally good positional accuracy. The machine writes the servo on the information medium by magnetic recording. This takes as long as six to eight minutes. Steps have been taken to spin the disk faster so that the write operation will take less time, but still it is a very expensive procedure to servo write a flexible disk. It has been suggested to print the servo track or stamp the servo track. This is often referred to as xe2x80x9cembossed servoxe2x80x9d. Embossed servo techniques are described in the following references: IBM TDB vol. 21, No. 10, xe2x80x9cFloppy Disc Embossing for Servo Applications,xe2x80x9d Acosta et al., 3/79 pp.4259-4260; xe2x80x9cEmbossed Servo Techniques for Floppy Discsxe2x80x9d, Thompson, et al., 1979, pp. 321-327; U.S. Pat. No. 4,935,835, Goodwin, et al., 4,958,425, Roth, et al.; 5,067,039 Godwin, et al.; 5,535,069, Chiao, et al.
It is an object of the present invention to smooth or flatten recording media for increased capacity flexible disk magnetic recording systems.
In accordance with the invention a magnetic recording disk is smoothed by positioning the disk between flat plates and increasing the temperature and pressure on the disk. Pressure is increased until the pressure approaches the yield strength of the substrate of the disk. Temperature is increased to above the glass transition temperature of the substrate, thereby allowing local deformation with low residual stress.
Further in accordance with the invention, one of the flat polished plates may be engraved with a servo pattern. When the disk is pressed between the flat plates, servo tracks are embossed on the media. The plates compress the media locally and plastically deform it. The disk is then passed through a magnetic field. The spacing over the embossed holes is so great that there is no magnetic signal in selected areas. This produces a magnetic servo track in an efficient manner.
The foregoing and other objects, features and advantages of the invention will be better understood from the following more detailed description and appended claims.